Twisted hair's tidy, but it provides no cover! (8,4)
I believe the answer is:
birthday suit
'it provides no cover' is the definition.
The definition suggests a singular noun which matches the answer.
'twisted hair's tidy but' is the wordplay.
'twisted' indicates an anagram.
'hairs'+'tidy'+'but'='hairstidybut'
'hairstidybut' is an anagram of 'BIRTHDAY-SUIT'.
Can you help me to learn more?
(Other definitions for birthday suit that I've seen before include "Nothing to wear?" , "State of total nakedness" , "Invisible threads?" , "State of being unclothed" , "Invisible outfit?" .)